How to check if the Workstation is locked?

function IsWorkstationLocked: Boolean;
var
  hDesktop: HDESK;
begin
  Result := False;
  hDesktop := OpenDesktop('default',
    0, False,
    DESKTOP_SWITCHDESKTOP);
  if hDesktop <> 0 then
  begin
    Result := not SwitchDesktop(hDesktop);
    CloseDesktop(hDesktop);
  end;
end;

Взято с сайта https://www.swissdelphicenter.ch/en/tipsindex.php